Typically, micro-fluidic capillary systems necessitate the use of capillary pumps. The capillary pumps have posts to create a capillary pressure inside the capillary system. An effective and efficient micro-fluidic capillary pumping system requires a high capillary pressure with a low-flow resistance. The dimensions of the posts of the capillary pump should be kept relatively small to create a high capillary pressure with a low flow resistance of the fluid.
In a capillary pumping application, the capillary pressure may be represented by ΔPcap=2γ/R, wherein γ is the liquid-vapor surface tension and R is the radius of curvature of the liquid-vapor interface. The radius of curvature ‘R’ is dependent on the geometry of the hydrophilic posts of the capillary pump. Therefore, the dimensions of the channel are kept small to provide a large capillary pressure. However, smaller channel dimensions result in the creation of viscous forces that result in an increase of the flow resistance of the fluid through the channel. Therefore, there is a trade-off between high capillary pressure and low flow resistance of a fluid.
Several solutions are suggested for overcoming the aforementioned drawbacks. One of the solutions is to use a plurality of parallel channels to reduce the flow resistance while maintaining a high capillary pressure. Another solution is to use a micro-pillar array. Both the aforementioned solutions may provide a high capillary pressure and a low flow resistance.
However, these solutions do not provide a reliable regular and controlled filling of the capillary pump. An irregular and uncontrolled filling of the capillary pump results in the creation of shortcut paths of a liquid in the capillary pump, whereby the fluid finds a direct path between an inlet and an outlet of the pump, without completely filling the pump. Further, the irregular and uncontrolled filling of the capillary pump results in the creation of air bubbles in a closed loop capillary pump resulting in a decrease of the volume of the capillary pump.
Hence, there is a desire for a capillary pump with a reliable controlled filling mechanism whilst achieving a high capillary pressure and a low flow resistance of a fluid sample in the pump. Further, there is a desire for a capillary pump with a reliable controlled filling mechanism to guide a fluid sample along a desired propagation path.
The abovementioned shortcomings, disadvantages, and/or problems are addressed herein and which will be understood by reading and studying the following description.